Some known steering columns for motor vehicles are provided with mechanisms for adjusting the steering column position by an operator of the motor vehicle. Available adjustments typically include a telescoping adjustment in which the steering column is extended toward the operator or retracted away from the operator, and a tilt or rake adjustment in which an angular position of the steering column is changed relative to the operator.
In some known systems, rake is adjusted by releasing an adjustment lever from a secured position, which then allows for rotation of the steering column about a pivot, typically located at an end of the steering column opposite that of the of the steering wheel. Returning the adjustment lever to the secured position retains the steering column in a desired set position about the pivot.
However, some traditional locks for steering columns may provide inadequate load handling capabilities for preventing upward steering column displacements in the event of a vehicle collision. Some prior attempts to address this issue have sought use of interlocking teeth to provide the required vertical stability. Unfortunately, however, many configurations that employ interlocking teeth to provide for a positive lock, while providing for selective engagement and disengagement of the teeth for alternating adjustment and locking of the steering column, encounter practical difficulties. For example, one source of dissatisfaction with such locking mechanisms is that the need to interlock the teeth of one component with the teeth of another may limit the available lock positions to a predefined finite set of positions. This issue provides a motivation toward decreasing the size of each of the teeth so as to decrease the incremental difference from one position to the next, providing for finer adjustments. Unfortunately, smaller teeth can result in decreased position assurance and loss of tactile sensations normally associated with the failure to securely seat the interlocking teeth. Other proposed solutions involve the use of frictions locks, which may provide more fine adjustments, but may sacrifice reliability, being susceptible to unintended releases (e.g., sliding adjustments, creep) under some loads.
Further, in a vehicle impact event, the steering column is configured to absorb energy of the impact to prevent or reduce injury to the operator due to collision with the steering wheel. In doing so, it is desired to further lock the rake position of the steering column to allow controlled energy absorption in such situations. In some steering column designs, during a collapse cycle, the column is designed to disengage the shaft and jacket assembly from the column mounting bracket. This allows the shaft and jacket assembly to shuttle forward in a vehicle, which allows the column to unclamp to facilitate internal collapse. At this point, rake lock needs to be maintained or re-established.
Accordingly, it is desirable to provide an energy absorbing rake lock assembly configured to establish rake lock during an impact event and to selectively fix and adjust a position of a steering column with improved fineness in the availability of adjustment positions and with improved reliability and security.